www.vesconite.com Long life, low friction, no swell

VESCONITERudder andStern tube bearings

Design Manual

22

What is Vesconite 1

Why use Vesconite 2

Classification Society Approvals 4

Vesconite Product Range 6

Vesconite - Chemical Resistance 8

Vesconite - Typical Properties 9

Interference Press Fits 10

Clearance for Rudder Bearings 10

Clearance for Water Lubricated Stern Tube Bearings 11

Outside Diameter, Inside Diameter 11

Wall Thickness 12

Grooves for Water Lubricated Stern Tube Bearings 12

Grooves for Rudder Bearings 12

Water Grooves 13

Design Loading 13

Length to Diameter Ratio 13

Machining Vesconite 14

Installing and Securing Vesconite 16

Housings 17

Mechanical Securing and Adhesive Bonding 17

Fitting Staves 17

Shaft and Other Mating Surfaces 17

Pressure and Velocity Limits 18

Field Trials 19

Company Profile 20

Warranty and Liability 20

Inquiry Service IBC

Contents

1

Under water or in humid conditions, Vesconite will not swell and seize which is a major problem with nylon bushes. Nor does Vesconite soften and wear in water like nylon. Vesconite's internal lubricantsmake it eminently suited to upper rudder bearing applica-tions where there are long

periods between greasing or no greasing at all, or where water lubrication cannot be ensured when operat ing with light ballasts. Since 1977 Vesconite has been proved and approved as a bearing material for marine applications. (See page 4)

What is Vesconite?VESCONITE is a specialised thermoplastic made from internally lubricated polymers. It has been proven since the late 1960s to be an exceptional plain bearing material, giving long life in applications where only the lowest rates of wear can be accepted. Even when conditions are dirty and unlubricated, Vesco nite gives long life together with low mainten ance and low friction.

Vesconite - with very low coefficients of friction whether dry or underwater, unlubricated or lubricated - is ideal for many marine applica tions. It is suited to both dry and immersed applications. In fact water is an excellent lubricant for Vesconite.

For rudder and stern tubebearings, Vesconite has many advantages compared to nylon, elastomers, phenolic laminates, lignum vitae and phos phor bronze.

Vesconite is dimensionally stable, unlike nylon, some elastomeric materials and phenolic laminates.

2

Why Use Vesconite?Vesconite combines the advantages of metallic and non-metallic bearings and bushes.

Vesconite is extremely versatile. It outperforms in most plain bearing applications, whether unlubricated, grease and oil lubricated, or water lubricated.

Long wear lifeVesconite gives up to 10 times the service life of phosphor bronze in poorly lubricated conditions.

Vesconite keeps size - no water swellVesconite does not swell. Vesconite is one of the most dimensionally stable synthetic materials available as shown in Figure 1. Vesconite bearings may be machined to the correct clearances

without fear of swelling. Clearances do not disappear. Vesconite gives you security!

For most synthetic bearing materials, water swell is a major problem. With water swell, there is always a risk of seizure. To compensate, suppliers of materials which swell advise excessive clearances.

Excessive clearances must be avoided for three reasons.

Firstly, they allow increased vibration.

Secondly, when machining an excessive clearance, one is machining away part of the wear life of the bearing - before installation!

Thirdly, and most negatively, the rate of wear of a sleeve bearing increases in proportion to the clearance.

The greater the clearance, the faster the bearing wears, which greatly shortens bearing life.

Vesconite remains hardIn a wet environment, Vesconite does not absorb moisture nor does it soften. Vesconite remains hard, and keeps its compression strength and excellent resistance to creep.

Many synthetic bearing materials, like those based on elastomers and nylons, soften and lose their compression strength in water. This is shown in Figure 2.

In the long term, humidity in the general environment leads to water absorption. Softening caused by humidity and immersed conditions has two major disadvantages for these materials.

Figure 1: Swell of synthetic bearing materials due to water

100

90

80

70

60

50

40

30

20

10

00.025 0.050 0.075

Vesconite

Cast Nylon

Elastomer

Strain

Stress in Mpa

Stress and straincomparison afterwater absorption.

Vesconite keepsits compressionstrength in wetenvironments.

Elastomers andnylons absorbmoisture, leadingto softeningand loss ofcompressionstrength.

100

90

80

70

60

50

40

30

20

10

00.025 0.050 0.075

Vesconite

Cast Nylon

Elastomer

Strain

Stress in Mpa

Stress and straincomparison afterwater absorption.

Vesconite keepsits compressionstrength in wetenvironments.

Elastomers andnylons absorbmoisture, leadingto softeningand loss ofcompressionstrength.

3

Firstly, the drop in compression strength leads to creep. If the bearing is reasonably loaded, it will squeeze out, and no longer hold the shaft in its proper location. Secondly, because the bearing surface is softer, its rate of wear increases dramatically, leading to a shorter bearing life.This is why Vesconite is the marine bearing material of choice - it remains hard in moist and immersed conditions, keeps its compression strength and maintains its excellent long life wear characteristics.

Vesconite does not delaminateVesconite is a homogenous bearing material without any lamination reinforcement. The result is that delamination cannot take place with

Vesconite, whereas it is a major problem for many laminated and composite products, for example laminated phenolics, laminated polyesters and thermosets.

What is delamination? Delamination is the peeling off of layers of the bearing. It is not a slow, steady process like wear - instead whole layers of the bearing break off, causing uneven and excessive clearance.

How does delamination occur? Laminated bearings are manufactured in layers, with a fibre or cloth reinforcement. As wear at the bearing surface occurs, water penetrates the exposed micro-channels that are formed by the cloth. Swelling occurs along these surfaces, causing weakness between the layers of the

laminate. The result is that the surface layers of the bearing material start peeling off.

Avoid delamination problems by switching to Vesconite.

Vesconite has low friction, even in actual working conditionsCompared to most elastomers, rubbers, nylons and laminates, Vesconite has a low friction. And this remains the case even in the practical, tough conditions of the real working environment.

Many products are claimed to have a low friction, but often only in the laboratory when tested under lightly loaded conditions, and before the effects of softening caused by water. Vesconite keeps its low static and dynamic friction whether dry or wet, or lightly or heavily loaded.

Figure 2: Vesconite maintains its compression strength whether wet or dry.

Visit vesconite.com to read more about the hundreds of vessels equipped with Vesconite during the last 25 years - ranging from pleasure boats to tankers - testifying to the desirability of long life, low maintenance Vesconite in marine applications.

Lloyd’sRegister Lloyd’sRegister

4

Classification Societies

Vesconite has approval from the world’s major shipping classification societies, including:

American Bureau of ShippingBiro Klasifikasi IndonesiaBureau VeritasChina Classification SocietyChina Corporation Register of ShippingDet Norske VeritasGermanischer LloydKorean Register of ShippingLloyd’s RegisterNippon Kaiji KyokaiRINA

Why is this important? Low friction for a rudder bearing means less bearing wear, as well as smoother operation and less wear to the whole steering gear.

The low static friction of Vesconite is especially beneficial to the low amplitude oscillating movements of rudders. With Vesconite every change of direction occurs smoothly, with a minimal power requirement and without any jerking.

Test this for yourself with Vesconite - its the best way to prove it. You will be delighted with the performance improvement compared to conventional materials.

SOS: Save Our ShaftsVesconite saves your shafts. Because of its low friction, most users report greatly reduced wear rates on shafts and liners. In many applications, users have switched to Vesconite because of the reduced wear, increased life and savings obtained on their shafts, often a very expensive component.

The case study of the propeller shaft bearings of the Jackson pilot boat on page 19 is an example of the low shaft wear rate.

If shaft wear is your problem, or you would like to extend your shaft life, contact us about options.

Vesconite does not corrodeVesconite is not subject to electrolytic corrosion, a major problem with traditional metallic bearing materials. While corrosion of the bearing surfaces is not normally a problem for bronze and cutless bearings, it becomes a major practical problem

when replacing a cutless or bronze bearing. Usually there is some corrosion between the outside of the bronze sleeve and the housing, which often makes removal of the old bearing exceptionally difficult.

Easy removal of Vesconite bearingsVesconite bearings are easy to remove. Since no electrolytic corrosion occurs with Vesconite, they do not seize like metallic bearings.

Vesconite does not contain any reinforcement, and old Vesconite bearings are easily removed. This is often not the case for laminated bearings: workers often struggle for hours trying to cut, hammer or burn laminated bearings out of their housings.

Safety and healthVesconite is a safe product. It does not contain asbestos or hazardous fibres. Nor does Vesconite contain any lead or hazardous substances.

Vesconite has passed a series of stringent health tests. It is fully approved for applications in direct contact with drinking water, both in cold and hot water.

Easy to machineCompared to metallic, cutless, bronze or synthetic bearing materials, Vesconite is very easy and safe to machine on standard metalworking and wood working machinery.

With Vesconite the size you machine is the size you get, unlike elastomers which stress relieve and change size during machining.

There are no dust or health problems when machining Vesconite, whereas these can

be problems with laminates as a result of the fibre reinforcement.

Low friction Vesconite keeps lathe tooling sharp hour after hour. This is another example of the long life, low wear properties of Vesconite. If machining a bearing blunts your tooling, think what it does to your shafts.

Vesconite versus white metalVesconite has a higher design load limit than white metal (babbitt), a higher fatigue strength and two to three times the wear life.

Chemical resistanceIn addition to its unrivalled performance in water, Vesconite has a wide range chemical resistance, including resistance to many acids, organic chemicals and solvents, hydrocarbons (including gasoline), oils and fuels. (See page 8)

If you need a bearing for a problem chemical application, contact us - we can advise whether Vesconite is suitable, or whether we can offer another of our speciality bearing materials.

5

www.vesconite.com for quick and easy to useonline design calculators

Vesconite Product Range

Vesconite is stocked in a wide range of sizes and shapes.

Vesconite can be obtained directly from dedicated dealerships in many parts of the world or airfreighted within days from the VescoPlastics’ factory.

Vesconite is available at short notice for special marine products, whether semi-finished or finished to toleranced drawings.

Special shapes may also be injection moulded in Vesconite for cost effective OEM components.

Bearings (Tubes) Stocked in 1 metre (39”) lengths for shafts from 6 to 650 mm diameter ( 1/4” to 26”).

Large diameter bearings (250 mm/10” and greater) are also stocked in 1.5 and 3 metre (5’ and 10’) lengths.

For greater economy these can be supplied to the length

required, thus avoiding wastage.

Details of the full bearing stock range may be obtained from your Vesconite dealer or by completing the inquiry form on the inside back cover of this manual.

Staves Vesconite staves for large rudder or stern tube bearings are cut and milled from plate.

Machined staves are produced in 1 metre (39”) lengths or as required up to 3 metre (10’) lengths.

Ready-to-Fit strut and rudder bearings with water grooves are stocked for shafts from 25mm (1”) to 50mm (2”) diameters and for housings from 40mm (11/2”) to 70mm (23/4”).

Outside diameters can be supplied to the nearest imperial size.

Ready-to-Fit Bearings

6

Linings Machining and lining of sleeves and housings can be undertaken.

Solid rods Diameters from 8 to 160 mm (5/16” to 6”) are stocked in 1 metre (39”) lengths.

Longer lengths may be produced upon request.

Thrust Washers Manufactured in diameters up to 715 mm (28”).

Plates andWear Strips

produced to required lengths. Standard plate widths are 200 mm (77/8”).

Some thicknesses are also available as plates 600 mm (231/2”) wide.

Available in accurately machined thicknesses from 3 to 50 mm (1/8” to 2”). Plates from 3 to 10 mm (0.118” to 0.394”) thickness are stocked in lengths up to 1000 mm (39”).

Plates from 12 to 50 mm (1/2” to 2”) thickness can be

Vesconite Superclad Bearings

Vesconite Superclad technology adds great versatility to the Vesconite stock range.

Many customers require special bearing sizes at short notice. To meet this need, a Superclad Vesconite bearing is produced.

A bearing with a suitable inside diameter is wound with a cloth membrane impregnated with an epoxy compound until the desired outside diameter is obtained.

Left to cure overnight, the bearing is ready for machining and despatch the next day.

The resulting Vesconite bearing is encased in a reinforced Superclad jacket, giving an extremely strong final structure.

The high strength of Superclad on the outside is combined with the good bearing properties of Vesconite on the inside.

Vesconite Superclad technology can quickly and economically produce bearings with practically any desired wall thickness for shafts up to 675 mm (261/2”) diameter.

7

Vesconite - Chemical Resistance

Vesconite has a wide range chemical resitance, including resistance to many acids, organic chemicals and solvents, hydrocarbons, oils and fuels, including gasoline.

If you need a bearing for a problem chemical application, contact us - we can advise whether Vesconite is suitable,

or whether we can offer another of our speciality bearing materials.

5% Acetic acid

10% Acetic acid

Acetone

Aniline

Benzine

Bleaching lye

Brake fluid

Butane

Butyl acetate

10% Calcium chloride

Calcium hypochlorite

Carbon disulphide

Carbon tetrachloride

40% Chromic acid

10% Citric acid

Cottonseed oil

25% Detergents

Dibutyl phthalate

Diesel oil

Dioxane

Ethanol

Ether (diethyl-)

Ethyl acetate

Ethylene dichloride

Freon II

5% Formic acid

Gasoline

Glycerol (Glycerine)

Glycol

Grease

Heptane

Hexane

10% Hydrochloric acid

5% Hydrofluoric acid

30% Hydrogen peroxide

Kerosene

Methanol

Methyl ethyl ketone

Mineral oils

Motor oils

10% Nitric acid

100% Oleic acid

Olive oil

Paraffin

Perchloroethylene

Petrol

30% Phosphoric acid

85% conc Phosphoric acid

10% Potassium chloride

10% Potassium dichromate

1% Potassium hydroxide

10% Potassium permanganate

Silicone fluids

1% Soap solutions

10% Sodium bicarbonate

10% Sodium bisulphite

20% Sodium carbonate

10% Sodium chloride

1% Sodium hydroxide

10% Sodium hypochlorite

30% Sulphuric acid

Toluene

Transformer oil

Turpentine

Vaseline

Vegetable oils

Water

White spirit

Xylene

Vesconite has good resistance to the following solutions at ambient temperatures

8

Density / Specific gravity 1.38 g.ml-1 1.38

Melting point 260°C 500°F

Hardness (Shore D) 84 84

Tensile strength at yield (D638) 65 MPa 9,400 psi

Tensile strength at break 62 MPa 9,000 psi

Elongation at break 26% 26%

Tangent modulus of elasticity (D790) 3400 MPa 493,000 psi

Flexural yield strength 120 MPa 17,400 psi

Deflection temperature at 1.85 MPa/268 psi 93°C 200°F

Modulus of elasticity under compression 2290 MPa 332,000 psi

Compression strength at yield 92 MPa 13,300 psi

Shear strength 49 MPa 7,100 psi

Notched impact strength charpy (D256) 33 J.m-1 0.6 ft-lb/in

Notched impact strength IZOD 16 J.m-1 0.3 ft-lb/in

Thermal conductivity 0.3 W.K-1.m-1 2 Btu-in/ft2/hr/°F

Coefficient of linear thermal expansion 6x10-5mm.mm-1.°C-1 3.3x10-5 in/in/°F

Maximum moisture absorption 0.5% 0.5%in water at 20°C/68°F

Equilibrium moisture absorption in air 0.2% 0.2%(50% relative humidity, 23°C/73°F)

Dynamic unlubricated friction 0.12 - 0.20 0.12 - 0.20coefficient on steel

Dielectric strength 14 kV.mm-1 360 kV/in

Gamma ray resistance 50% loss of properties 100 Mrads 100 Mrads

Physical properties may be altered to some extent by processing conditions.

Vesconite - Typical Properties

9

Example: A rudder pintle has a diameter of 508mm (20”) Find the fitted minimum clearance?From Fig. 4 fitted running clearance is 0.96mm (0.038”)

Example: A rudder neck bearing is required for a housing of 533 mm (21”). The bearing will be machined in a workshop with an ambi ent temperature of 20°C (70°F). The bearing may oper ate in temperatures as low as -20°C (-4°F). Specify the press fit required.Using -20°C (-4°F) line in Figure 3, press fit = 1.86 mm (0.073”)

10

Designing Bearings

InterferencePress FitsInterference press fits are the most common method for securing Vesconite bearings.

The press fits recommended for most applications may be read off Figure 3. The graph assumes a bearing ambient temperature of 20°C (70°F) when it is machined.

Choose the press fit required for the minimum operating temperature of the bearing.

If a lower operating temperature is anticipated, contact your authorised Vesconite distributor.

Clearance forRudder Bearings The recommended running clearances for rudders after fitting in well aligned housings under normal conditions are given in Figure 4.

No extra clearance is needed to allow for water absorption before entering service. Vesconite does not absorb water to any appreciable extent, unlike many other synthetic materials which swell as they absorb water.

Figure 3: Press fits for rudder and stern tube bearings

Figure 4: Fitted running clearance for rudder bearings

Example: For a water lubricated stern tube bearing used for a 356 mm (14”) propeller shaft, find the fitted minimum clear ance.From Figure 5, the required running clearance after fittingis 0.91 mm (0.036”).

11

Designing Bearings

Clearance for Water Lubricated Stern Tube Bearings

The recommended fitted running clearance for water lubricated stern tube and strut bearings in well aligned housings is obtained from Figure 5.

Figure 5: Fitted running clearance for water lubricated stern tube bearings

Outside DiameterThe bearing outside diameter is obtained by adding the press fit to the maximum diameter of the housing.

Inside DiameterThe free standing bearing inside diameter is obtained by adding the maximum shaft diameter, the press fit multiplied by housing diameter ,

shaft diameterand the running clearance.

When press fitted, the bearing inside diameter is reduced by an amount somewhat greater than the press fit. Hence the press fit is multiplied by housing diameter .

shaft diameterThis is called bore closure.

ID = shaft dia. + running clearance + ( press fit x )housing dia.shaft dia.

OD = housing diameter + press fit

Lead-in chamfer

Bearingoutsidediameter

Interference

Housingdiameter

Runningclearance

Wallthickness

Bearinginsidediameter

Shaftdiameter

Example: A water lubricated stern tube bearing fits into a 254 mm (10”) housing. The stern tube is designed to carry a 203.2 mm (8”) shaft. The bearing will be machined in a work shop with a tem perature of 20°C (70°F).From Figure 3, the bearing requires a press fit of 0.56 mm (0.022”). Thus outside diameter = 254 + 0.56 mm [10” + 0.022”] = 254.56 mm [10.022”]

To find the inside diameter we require the clearance.

From Figure 5 the running clearance is 0.6 mm [0.024”]Thus inside diameter = 203.2 + 0.56 x 254 + 0.6 mm 203.2 = 204.5 mm

[ 8” + 0.022” x 10” + 0.024” = 8.052” ] 8”

Wall thickness = 0.5 ( 254.56 - 204.5) = 25.03 mm

[ 0.5 (10.022” - 8.052”) = 0.985”]

12

Wall ThicknessWhen machining, it is best to specify and control the bearing outside diameter and wall thickness.This is because workshop temperature changes can

cause expansion and contraction of up to 0.1%.

For example a 10°C (18°F) temperature change on a 500 mm (20”) diameter bearing will result in a diameter change of 0.3 mm

(12 thousandths) on a free standing bearing.

If the wall thickness is controlled, diameter changes will not affect the running clearance once the bearing has been press fitted.

Calculate the wall thickness as follows: Wall thickness = 0.5 [ OD - ID ]

Grooves for Rudder Bearings Generally Vesconite rudder bearings do not need water circulation grooves. Vesconite is also suited to unlubricated

operation when the movement is slow or intermittent which is the case in most rudder applications.

Initial and occasional greasing of Vesconite rudder bearings is advantageous as it increases

bearing life, and grooves may be provided for this purpose.

If grooves are machined into rudder bearings, groove depth should not exceed one third of the Vesconite wall thickness.

Grooves for Water Lubricated Stern Tube BearingsTable 1 gives details of the water grooves and flow rates recommended for water lubricated bearings.

Do not grease water lubricated Vesconite stern tube bearings. Grease may

block the water grooves and interfere with water flow.

If more than one bearing is used, radial recesses around the inner circumferences where the bearings join must be provided to ensure water flow even if the water grooves are not aligned.

A positive pumped flow of engine cooling water to the

inboard end of the bearings is recommended to prevent abrasive particles entering the bearings, especially when operating in sandy conditions or on rivers.

If engine cooling water is used, the water temperature should not exceed 55°C (130°F) to avoid possible hydrolytic degradation of Vesconite over a long period of time.

Designing Bearings

Example: A 500 mm (20”) long bearing with an internal diameter of 400 mm (16”) can support a load of 50 cm x 40 cm x 300 kg.cm-2 [ 20” x 16” x 4,400psi ]= 600 000 kgs [1, 408,000lbs ],that is 600 metric tons.

Shaft diameter No. of *Angle Groove width Groove depth Waterflow rate grooves between mm inches grooves mm inches mm inches ll min-1 gal/min

60-79 2-3 7 45° 7 0.25 4 0.15 12 3.0

80-119 3-5 7 45° 9 0.30 5 0.20 18 4.5

120-159 5-6 7 45° 10 0.35 6 0.25 24 6.0

160-199 6-8 7 45° 12 0.40 7 0.30 30 8.0

200-249 8-10 7 45° 12 0.40 8 0.30 38 10.0

250-299 10-12 7 45° 14 0.50 8 0.30 45 12.0

300-349 12-14 8 40° 15 0.50 8 0.30 53 14.0

350-399 14-16 8 40° 15 0.50 8 0.30 60 16.0

400-499 16-20 9 36° 15 0.50 9 0.35 75 20.0

500-599 20-24 10 33° 18 0.50 9 0.40 90 24.0

600-699 24-28 11 30° 18 0.50 9 0.40 105 28.0

700-800 28-32 12 27° 18 0.50 9 0.40 120 32.0

13

Table 1: Groove sizes and flow rates for water lubricated stern tube bearings

‘UV’ groove design and recess if more than one bearing is used

* It is recommended that no groove be located in the 6 o’clock position.

Designing Bearings

Design Loading

Length to DiameterRatio of Stern Tube Bearings

Traditionally, water lubricated stern tube bearings have been designed with a bearing length equal to four times the shaft diameter. Because of the high

load capabilities of Vesconite, this bearing surface is more than adequate. In many applications, shorter length bearings may be used.

Vesconite is a high compression strength, low creep material. The compression strength of Vesconite at yield is over 90 MPa (13,000 psi). This allows for static design loads of up to 30 MPa (300 kg.cm-2) (4,400 psi) provided the bearing is supported within a rigid housing.

The ‘UV’ groove design with a round groove base and a chamfered edge is recommended as it maintains a better hydrodynamic water film. Groove depth should not exceed half the Vesconite wall thickness. ‘UV’ groove

14

Vesconite XL bearings are easily machined on standard lathes if proper support is provided to prevent deformation and cracking.

When machining a large bearing, the machinist has many options, depending on the diameter and length of the bearing and the lathe or boring mill available.

By taking the following important precaution, the machinist will find Vesconite bearings a pleasure to machine:

When chucking the bearing, always use an inside support disc machined size-for-size to the bearing inside diameter to prevent possible cracking.Machine the support from a steel plate, disc or washer, 25 - 35 mm (1 - 11/2") thick.

Do not clamp Vesconite like a metal, but clamp gently and with care to avoid distortion.

Machining Vesconite

1 Align and face one end

of the bearing square. (A) This helps with alignment

later. Use the internal support

disc machined to size to prevent distortion and cracking.

2 Swop bearing around,

align and face the other end. (B)

Again use the disc to support the inside diameter.

5 Switch bearing around

to part to length.

A new disc machined size-to-size with the final bearing inside diameter will be required for support.

3 Machine the outside

diameter of the bearing, again with the support disc in place.

4 Machine the inside

diameter, again with the support disc in place.

When taking rough cuts, measure wall thickness as a check on accuracy and ovality.

If more than 15mm ( 3/4") has to be removed from either the outside or inside diameters of the bearing, first semi-finish both the inside and the outside diameters to approximately 5mm ( 1/4") oversize.

When machining large bearings ensure that the free end of the bearing is suitably supported.

For best internet support and online design calculatorswww.vesconite.com

Larger diameter support disc, machined size-to-size with final bearing inside diameter.

Support disc,machined to size.

B A

A B

A B

B A

A B

Outside diameter tolerance Wall thickness tolerance% of outside diameter % of wall thickness

+0.2% +0.0%

-0.0% -0.5%

Machining TolerancesThe following are acceptable tolerances for the bearing outside diameter and wall thickness:

Top rake0° - 5°

Front clearance 5° - 11°

200 mm300 mm400 mm500 mm600 mm700 mm

8”12”16”20”24”28”

Machining Grooves on Centre Lathes

17

Machining Vesconite

Use a tool up to the width of the groove required in a boring bar. Lock the chuck into position.

Move the tool through the bearing using the hand wheel

or rapid advance taking a cut up to 1.5 mm ( 1/16”) maximum at a time until the required groove depth is obtained.

Cutting SpeedsUp to 300m (1000’) per minute

Cutting FeedsRough: 0.5 - 0.7mm (0.020 - 0.030”) per revolution

Finish: 0.3 - 0.4mm (0.012 - 0.016”) per revolution

Turning Speed Guidelines: Bearing outside diameter RPM

35030020015010070

Tool Cutting Angles

15

Cutting ToolsUse sharp high speed tools or tungsten carbide tips with high clearances and positive rake angles. Rough cuts up to 5 mm ( 1/4") deep may be taken, with a finishing cut of at least 1 mm ( 1/32").

Allow the bearing to cool before taking final cuts.

Side rake 5° - 11°

16

Freeze fitting is the easiest way to install Vesconite bearings. Dry ice is an ideal agent but liquid nitrogen can be used if dry ice is not available.

Using Dry IceVesconite has a thermal expansion coefficient of 6 x 10-5 mm/mm/°C (3.3 x 10-5 in/in/°F).

Cooling in dry ice for two to three hours reduces bearing temperatures by 40 to 60°C (70 to 100°F). This results in a shrinkage of 1,2 mm (0.05”) on a 500 mm (20”) diameter bearing.

Good ventilation must be used in confined spaces to avoid possible lack of air.

Using Liquid NitrogenUse an insulated container as shown below. The container may be any suitably sized metal drum. To insulate, simply wrap around with glass or rock wool, or several layers of corrugated cardboard, or bubble wrap. These may be held in place by tape, wire or strapping.Place the bearing on wooden blocks or bricks to raise it 150 mm (6”) above the bottom of the container. Do not place the bearing directly onto the floor of the container.Place a loose fitting lid on top of the container. If the lid is made from chipboard or plywood 18 to 25 mm thick (0.75” to 1”), it will act as an insulator as well. Slowly pour liquid nitrogen into the bottom of the container - about 50 mm (2”) deep.Only sufficient liquid nitrogen to cover the bottom of the container is needed.

It is important to ensure that the liquid nitrogen does not come into direct contact with the Vesconite bearing.Allow the bearing to cool for approximately 1 to 11/2 hours which should be enough to shrink it sufficiently for a sliding fit.

Measure the top outside diameter with a vernier to ensure that sufficient shrinkage has occurred before removing the bearing from the container.

Use nitrogen only in well ventilated areas. Take care in handling and adhere to the general safety rules for liquid nitrogen as it can cause severe burns. Consult your supplier of liquid nitrogen for detailed precautions. Safety visors and protective clothing should be used.

Installing and Securing Vesconite Bearings

Vesconite bearingpacked in a container with dry ice.

Vesconite bearingpacked in a container supported bywooden blocks100-150 mm(4-6”) high.

Insulationmaterial

Lid

Liquidnitrogen up to 50mm deep

Ensure that liquid nitrogen does not come into direct contact with Vesconite bearing.

17

Housings While Vesconite is a fairly rigid material, it will generally conform to the size and shape of the housing. Therefore out-of-round or out-of-line

housings should be avoided, unless the housing is made round or in-line through machining.

Mechanical Securing

Adhesive Bonding

Fitting Staves

Installing and Securing Vesconite Bearings

As a standard safety precaution, bearings should always be secured using conventional mechanical means such as keeper rings. Grub screws may be used on small bearings.

Mechanical securing to prevent possible rotation and end keeper rings are especially important for bearings that may be used in sub-zero conditions.

If desired, anaerobic adhesives such as Loctite 603 or 648 retaining compound may be used. Adhesive bonding is recommended when using sliding fits.

Machine a lead in chamfer of 15° to 35° on the leading edge of the bearing. Prime

initially with Loctite Primer T and allow to dry.

Loctite 603 or 648 (former for smaller gaps and the latter for larger gaps) should be applied to both the Vesconite bearing and metal housing surfaces. The bearing should be pressed into place and excess adhesive wiped off.

Shaft and Other Mating Surfaces

Metal mating surfaces must be suited to the wear conditions encountered, for example when operating in sandy conditions. Hard shaft surfaces ensure longer shaft and bearing life.

Hardchrome plated surfaces, seawater corrosion resistant stainless steel and admiralty and gunmetal bronze liners are generally satisfactory as mating surfaces for Vesconite.

Carbon steel and hardened steel shafts may be used as mating surfaces provided that they do not corrode under the conditions of use. A good finish of the order of 0.5 micrometre Ra (20 micro-inches Ra) should be provided on shaft surfaces.Rough surface finishes and corroded and scored shafts will cause wear of Vesconite bearings and should be avoided.

Fitting of Vesconite staves is facilitated by cooling the staves in dry ice for 3 hours before fitting.

Grub screw

Edge wellchamfered

Keeper plate

18

Pressure x Velocity(PV) Limits

All bearing materials have limits in their ability to sustain a given loading at a particular speed. This is known as the pressure x velocity limit or PV limit.

Apart from pressure and velocity, the PV limit of Vesconite depends upon operating conditions. The most significant factors in

operation are whether friction is reduced through water or oil lubrication, and whether heat removal occurs either through circulating water or oil.

The recommended PV limits for Vesconite are given in Table 2. If your application has PV values higher than those shown, consult your dealer or the manufacturer.

PV limit

Operating condition MPa.m.min-1 psi-ft/min

Dry - no lubrication 5 2,500

Greased on assembly 10 5,000

Lubrication at regular intervals 20 10,000

Circulating oil lubrication 40 20,000

Circulating water lubrication 200 100,000

Table 2: Recommended Vesconite PV limits

Photograph: Safmarine

19

Field Trials of Vesconite Stern Tube Bearings

The very long service life of Vesconite stern tube bearings is demonstrated by 25 years of experimental and survey results obtained from the RP Jackson, a harbour pilot cutter.

The RP Jackson has two 145 mm (5.7”) propeller shafts held by A frames with bearings 550 mm (21.6”) long.

The RP Jackson sails in and off Durban harbour under fairly severe conditions. These waters invariably contain relatively high concentrations of abrasive, suspended sand particles arising mainly from propeller wash.

Superior wear figures were

obtained. Strut bearing wear of between 1.5 and 3.0 mm (60 and 120 thousandths) was measured after each 5 year period of service, equivalent to 0.4 mm (20 thousandths) wear per year.

The observed wear figures were remarkably low given the sandy harbour waters the RP Jackson operates in.

An advantage of Vesconite bearings confirmed in the RP Jackson trials was that the wear on the propeller shaft lining was reduced substantially.

The RP Jackson, operating on Vesconite bearings for over 25 years.

20

Company Profile

Vesconite is produced in what is probably the largest factory of its kind in the world, dedicated to the development, production and application of

internally lubricated thermoplastic bearing materials.

VescoPlastics - the developers and manufacturers of Vesconite - have been involved in the production of bearing materials, anti-wear

and anti-friction processes, as well as precision engineering since the 1950’s. It is a company with a long tradition of developing products and techniques for problem solving where quality and service are the chief concerns.

Limited Warranty and Limitation of Liability

1 This design manual is based upon many years

of experience of VescoPlastics (the Company) in manufacturing and installing Vesconite.

Experience shows that no two applications are the same in every detail so the Company encourages that every

application be treated as individual and unique.

This information is offered in good faith as part of our client service, but favourable results cannot be guaranteed. This manual is intended for use by persons with technical skill, at their discretion and risk. The purchaser must determine the suitability of the goods for their intended purpose.

2 The Company reserves the right to change or

amend any recommendation or specification without notice.

3 Goods are supplied on the express condition

that the Company’s liability is limited to the replacement of defective goods or materials.

4 The Company does not hold itself responsible

for any damage, incidental or consequential loss suffered as a result of the use of goods supplied.

5 Acceptance of goods will be held to imply

agreement to the above conditions.

IBC

Inquiry ServiceYou will be surprised to learn how competitively priced Vesconite bearings are. For a free quote, fax the following details to Vesco Plastics Sales (+27 11) 616 2222 or (+27 11) 615 3810.

Bearing Application

Rudder/Pintle bearings Other (specify) ........................

Stern tube/Strut/V-bracket ............................................... (water lubricated)

Dimensions mm’s inches

Shaft diameter ................................................

Housing diameter ...........................................

Bearing length ...............................................

Customer Details

Inquiry from ..........................................................................................................

Address ................................................................................................................

..............................................................................................................................

Country ............................................... Postal code ............................................

Telephone ........................................... Fax..........................................................

E-mail ................................................. Website...................................................

Visit www.vesconite.comfor information on Vesconite applications in numerous industries including marine, pumps, water treatment, sewage, fish farming, hydro-electric, mineral processing.

Order Design Manuals online or use our Marine Design-a-Bearing calculator program for instant answers to your design questions.

P O Box 40647, Cleveland, 2022 South Africa Tel (+27 11) 616-1111 or 616-4444 Fax (+27 11) 616-2222 or 615-3810 e-mail: vesconite@vesconite.com

www.vesconite.com

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